var sessionrequest = null;
    var interval = 1320000;
    function createSessionRequest() {
    try {
         sessionrequest = new XMLHttpRequest();
        } catch (trymicrosoft) {
            try {
            sessionrequest = new ActiveXObject("Msxml2.XMLHTTP");
            } catch (othermicrosoft) {
                try {
                sessionrequest = new ActiveXObject("Microsoft.XMLHTTP");
                } catch (failed) {
                  sessionrequest = null;
                 }
             }
        }
   }

    function getNewSession()
    {
        
        createSessionRequest();
        var url = 'renew.aspx?dm=' + new Date().getTime();
        sessionrequest.open("GET",url,true);
        sessionrequest.onreadystatechange = sessionupdatepage;
        sessionrequest.send(null);
        
        
    }
    function sessionupdatepage()
    {       
       
    }
    
    setTimeout(function(){setInterval(function(){getNewSession()},interval)},interval);